Nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water, and preparation method and application thereof

Abstract

The application provides a nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water and a preparation method and application thereof, and belongs to the technical field of hydrogen production by alkaline electrolysis of water. In view of the problems of the existing nickel-molybdenum alloy catalyst, such as easy dissolution of Mo in an alkaline medium, poor stability, dependence on a substrate, and complex preparation, the application constructs a core-shell structure of RE-MoO 3‑x 3‑x by means of trace RE doping, coprecipitation and reduction atmosphere annealing, wherein the core is a Ni4Mo alloy, and the surface is coated with an RE-MoO 3‑x shell layer. The shell layer accelerates water hydrolysis and produces a synergistic effect with the Ni4Mo core to drive hydrogen intermediates to migrate to the core to realize efficient hydrogen evolution, and the Mo-O-RE bond formed can anchor Mo and inhibit the dissolution thereof. When the catalyst is used for hydrogen production by alkaline electrolysis of water, the overpotential is as low as 53 mV in 1M KOH at a current density of 10 mA / cm 2 , and the catalyst can be stably operated for more than 300 hours, and has high activity, high stability and simple preparation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hydrogen production by alkaline electrolysis of water, and relates to an electrolysis process or electrophoresis process technology for producing compounds or non-metals, an electrode comprising one or more electrocatalytic coatings on a substrate, an electrocatalyst composed of at least one catalytic element and at least one catalytic compound, and a RE-MoO 3-x shell layer, and particularly to a nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water, and a preparation method and application thereof. BACKGROUND

[0002] In the process of global energy transformation, hydrogen energy has become one of the core development directions due to its high energy density and clean environmental characteristics. Among them, hydrogen production by electrolysis of water is considered as a key technology for producing green hydrogen due to its simple and efficient process. Although the hydrogen evolution reaction (HER) involves only two electron transfers, the kinetic process is slow, and a highly efficient HER catalyst is needed to reduce the reaction energy barrier and improve the reaction rate.

[0003] In an alkaline medium, the HER reaction usually includes an initial water dissociation process (Volmer step: H2O + e - → H ad + OH - ) and a subsequent hydrogen desorption process. Among them, the hydrogen desorption process can be carried out through two pathways: (1) Heyrovsky step: H2O + e - + H ad → H2 + OH - ; (2) Tafel step: 2H ad → H2. However, the high water dissociation energy barrier in the Volmer step and the existence of the strong covalent bond H-O-H seriously hinder the effective transfer of protons and the generation of hydrogen intermediates (H ad ), which not only inhibits the subsequent steps, but also occupies the active sites of the catalyst, ultimately leading to a significant reduction in overall catalytic activity. Although platinum (Pt) based catalysts have excellent HER activity, their high cost and resource scarcity limit their large-scale commercial application. Therefore, it is of great significance to develop efficient and low-cost non-noble metal hydrogen evolution catalysts.

[0004] Nickel-molybdenum alloy (NiMo) is considered as a potential material to replace Pt-based catalysts due to its excellent electrical conductivity and suitable hydrogen adsorption energy, but its catalytic performance still lags behind that of Pt and has the problem of poor structural stability: Mo is easily oxidized in alkaline electrolyte and dissolved in the form of MoO4 2- , which seriously restricts the electrochemical performance and stability.

[0005] To address this challenge, researchers have attempted to control the electronic structure and hydrogen adsorption energy of alloys by doping with metal or non-metal elements, which has significantly improved catalytic activity, but the core problem of stability has not been solved. To solve this problem, existing technologies attempt to improve performance through element modification. For example, Chinese Patent Application CN117702164A discloses a rare earth element modified molybdenum-containing catalyst, which builds a catalytically active layer on a transition metal substrate and uses rare earth elements to form compounds with molybdenum to inhibit molybdenum leaching. However, this technology has the following shortcomings:

[0006] (1) The catalyst structure is dependent on a specific substrate, with the catalytically active layer grown on the surface of a pre-made substrate, limiting the flexibility and application range of the catalyst, and unable to adapt to various electrode forms.

[0007] (2) The preparation process is complex, involving multiple steps such as hydrothermal reaction, impregnation, and calcination, making the process cumbersome and not suitable for large-scale production.

[0008] (3) The mechanism is not fully explained: although a rare earth-molybdenum compound phase (such as Sm2Mo2O9) is formed, the mechanism of rare earth modification on the electronic structure and reaction kinetics is not fully revealed, especially the synergistic promotion of water dissociation and hydrogen adsorption-desorption processes.

[0009] (4) Cost and efficiency are insufficient: the amount of rare earth elements used in Chinese Patent Application CN117702164A is high, and the preparation cost of the substrate-based catalyst is high, making it difficult to meet commercialization needs.

[0010] Therefore, there is an urgent need to develop a nickel-molybdenum-based catalyst with flexible structure, simple preparation, clear mechanism, and high activity and stability, to promote the practical application of alkaline electrolytic water hydrogen production technology. SUMMARY

[0011] The present invention is aimed at overcoming the shortcomings of existing catalysts, such as poor stability, complex preparation, and substrate dependence, and provides a nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolytic water hydrogen production, as well as a preparation method and applications. Through innovative core-shell structure and trace rare earth doping strategies, the unification of high activity and high stability of the catalyst is achieved, providing strong support for the commercialization of alkaline electrolytic water hydrogen production technology.

[0012] The application provides a preparation method of a nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water, which has the following characteristics and comprises the following steps: S10, dissolving nickel salt, molybdate and a rare earth metal source in a mixed solution of ethylene glycol containing ammonia water according to a molar ratio of 2:0.5:(0.035-1) to obtain a precursor solution with a rare earth metal source concentration of 0.5 mol / L-1.0 mol / L, wherein the rare earth metal source comprises any one or more of yttrium salt, lanthanum salt, scandium salt or cerium salt, and the NH3 concentration in the precursor solution is 0.5 wt%-1.0 wt%; S20, performing a coprecipitation reaction on the precursor solution at 100-200 DEG C for 15-60 min, and then separating the precursor RE-NiMoOH; S30, annealing the dried fine powder-shaped precursor RE-NiMoOH in a reducing atmosphere at 300-500 DEG C for 1-2 h to obtain a Ni4Mo@RE-MoO 3-x As the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water, the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water has a Ni4Mo alloy core and an oxygen vacancy-rich RE-MoO 3-x shell layer.

[0013] Preferably, in step S10, the rare earth metal source concentration in the precursor solution is 0.75 mol / L-0.96 mol / L.

[0014] Preferably, in step S10, the nickel salt comprises nickel nitrate, the molybdate comprises ammonium molybdate, the yttrium salt comprises yttrium nitrate, the lanthanum salt comprises lanthanum nitrate, the scandium salt comprises scandium nitrate, and the cerium salt comprises cerium nitrate.

[0015] Preferably, in step S10, the rare earth metal source is yttrium salt, and the molar feeding ratio of the nickel salt, the molybdate and the rare earth metal source is 2:0.5:(0.035-0.045).

[0016] Preferably, in step S10, the NH3 concentration in the precursor solution is 0.85 wt%-0.90 wt%.

[0017] In the preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water provided by the application, the following characteristic can also be possessed: in step S10, the ethylene glycol concentration in the precursor solution is 80 wt%-90 wt%.

[0018] Preferably, in step S10, the ethylene glycol concentration in the precursor solution is 87.4 wt%-87.8 wt%.

[0019] Preferably, in step S20, the co-precipitation reaction conditions are: heating at 145 ℃~155 ℃ for 25 min~30 min.

[0020] In the preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water provided by the present application, it can also have the following features: in step S20, the separation method is: after cleaning with anhydrous ethanol, vacuum freeze-drying and grinding to fine powder.

[0021] In the preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water provided by the present application, it can also have the following features: the vacuum freeze-drying temperature is-60 ℃ to-70 ℃, and the time is 12 h~15 h.

[0022] Preferably, the vacuum freeze-drying temperature is-70 ℃, and the time is 12 h.

[0023] Preferably, in step S30, the annealing conditions are: annealing at 380 ℃~420 ℃ for 1 h~1.2 h in a reducing atmosphere.

[0024] In the preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water provided by the present application, it can also have the following features: in step S30, the reducing atmosphere is a mixed gas of hydrogen and argon, and the hydrogen concentration in the mixed gas is 0.2 wt%~0.6 wt%.

[0025] Preferably, the hydrogen concentration in the mixed gas is 0.55 wt%.

[0026] In the preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water provided by the present application, it can also have the following features: in step S30, the annealing temperature is 400 ℃.

[0027] Preferably, the annealing temperature is 400 ℃.

[0028] Preferably, the annealing temperature is 400 ℃.

[0029] The present application also provides a nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water, which is prepared by the preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to any one of the preceding embodiments.

[0030] The application further provides application of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water in hydrogen production by alkaline electrolysis of water, wherein the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water is coated on a substrate, so as to serve as a working electrode in hydrogen production by alkaline electrolysis of water together with the substrate.

[0031] The nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water, the preparation method and the application thereof have the following beneficial effects:

[0032] (1) The nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water has high catalytic activity and low overpotential: due to the synergistic effect of the core-shell structure, the RE-MoO 3-x shell layer significantly accelerates the water dissociation kinetics (Volmer step), and the directional electron transfer (Mo→Ni) at the core-shell interface drives the hydrogen intermediate (H ad ) to migrate to the Ni4Mo core, realizing efficient hydrogen adsorption-desorption. This synergistic mechanism significantly reduces the reaction energy barrier, making the catalyst exhibit excellent hydrogen evolution activity. In a 1 M KOH electrolyte, the overpotential of the catalyst of the application is as low as 53 mV at a current density of 10 mA / cm 2 , which is superior to the catalyst performance reported in the prior art Chinese patent application CN117702164A and close to the level of commercial Pt / C.

[0033] (2) The nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water has significant long-term stability: by forming stable Mo-O-RE bonds, the molybdenum element is effectively anchored, solving the poor stability problem of traditional NiMo alloys in alkaline solution due to Mo dissolution, so that the catalyst remains stable in performance under high current density for a long time, significantly prolonging the service life. The catalyst of the application can be stably operated for more than 300 hours at a current density of 10 mA / cm 2 , while the catalyst in the prior art Chinese patent application CN117702164A can only maintain for several hours under the same conditions, indicating that the nickel-molybdenum-based rare earth element doped core-shell catalyst of the application has a significant advantage in solving the problem of molybdenum dissolution.

[0034] (3) The structure of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water is flexible and widely applicable: the catalyst of the application is in the form of a nano-sized powder and is not dependent on a specific substrate, and can be flexibly matched with various electrode materials (such as carbon paper, nickel foam, etc.), greatly expanding its application scenarios, while the catalyst in the prior art Chinese patent application CN117702164A is limited to a preformed substrate and lacks flexibility in application.

[0035] (4) The preparation process of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis water is simple and low in cost: a two-step method of coprecipitation-reduction annealing is adopted, without complex hydrothermal or impregnation steps, simple and controllable operation, without complex equipment, and mild and controllable reaction conditions. At the same time, only a small amount of rare earth elements (such as Y, La, Sc, Ce) is used, which is much lower in cost than noble metal catalysts (Pt-based catalysts), and has significant economic benefits, providing a feasible solution for the low-cost commercial application of alkaline electrolysis water hydrogen production catalysts.

[0036] (5) The mechanism of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis water is clear and has scientific innovation: through XPS, EPR and other characterization means, the electron transfer and oxygen vacancy formation mechanism induced by rare earth doping are clarified, and the synergistic promotion effect of the core-shell structure on the reaction kinetics is revealed, providing a new idea for the design of alkaline electrolysis water catalysts.

[0037] (6) The strategy of introducing strong oxygenophilic rare earth elements (RE) presents significant technical advantages, and the rare earth oxides can act as high-efficiency water dissociation active sites to accelerate the slow Volmer step, and the electronegativity of the rare earth elements is much lower than that of Ni, which is easy to form a stable Mo-O-RE bond structure with Mo.

[0038] (7) The present application prepares a Ni4Mo@RE-MoO 3-x core-shell structure catalyst by doping a small amount of rare earth elements, and the Mo-O-RE bond formed in the catalyst can enhance the stability, and the RE-MoO 3-x shell layer interface can accelerate the water dissociation process and form a synergistic effect with the Ni4Mo alloy core, thereby significantly improving the HER performance. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is a flowchart of a preparation method of a nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis water according to an embodiment of the present application.

[0040] Figure 2 is an XRD pattern of catalyst 1, comparative sample 1 and comparative sample 2 of test example 1 of the present application.

[0041] Figure 3 is an SEM image of catalyst 1 of test example 1 of the present application.

[0042] Figure 4 is a TEM image of catalyst 1 of test example 1 of the present application.

[0043] Figure 5 is an XPS pattern and an EPR pattern of each element in catalyst 1 and comparative sample 1 of test example 1 of the present application.

[0044] Figure 6 is the LSV test curve of the working electrode provided by catalyst 1, catalyst 2, catalyst 3, catalyst 4, commercial 20% Pt / C in Test Example 2 of the present application.

[0045] Figure 7 is the LSV test curve of the working electrode provided by catalyst 1, catalyst 5, catalyst 6, catalyst 7, commercial 20% Pt / C in Test Example 2 of the present application.

[0046] Figure 8 is the LSV test curve of the working electrode provided by catalyst 1, commercial 20% Pt / C, comparative sample 1, comparative sample 2 in Test Example 2 of the present application.

[0047] Figure 9 is the hydrogen evolution stability test curve of the working electrode provided by catalyst 1, catalyst 5, catalyst 6, catalyst 7, comparative sample 1, comparative sample 2 in Test Example 3 of the present application. DETAILED DESCRIPTION

[0048] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the following embodiments will be specifically described in combination with the drawings for the nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolysis of water to produce hydrogen and a preparation method and application thereof.

[0049] EMBODIMENT

[0050] Figure 1 is a flowchart of the preparation method of a nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolysis of water to produce hydrogen according to the embodiment of the present application.

[0051] As shown in Figure 1 , the present embodiment provides a preparation method of a nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolysis of water to produce hydrogen, which comprises the following steps:

[0052] S10, dissolving the nickel salt, molybdate and rare earth metal source in the mixed solution of ethylene glycol containing ammonia water to obtain a precursor solution, and the specific operation is as follows:

[0053] A certain amount of nickel salt, molybdate and rare earth metal source is weighed and added to a round-bottom flask, and then 5 mL of water, 45 mL of ethylene glycol and 2 mL of 28 wt% ammonia water are added in sequence, and magnetic stirring is performed for 30 min until complete dissolution to form a uniform precursor solution.

[0054] Among them:

[0055] (1) The molar ratio of the nickel salt, molybdate and rare earth metal source is 2:0.5:(0.035~1).

[0056] (2) In the precursor solution: NH3 concentration is 0.88 wt%; ethylene glycol concentration is 87.6 wt%.

[0057] (3) The nickel salt includes nickel nitrate (in this embodiment, specifically, nickel nitrate hexahydrate is selected).

[0058] (4) The molybdate salt includes ammonium molybdate (in this embodiment, specifically, ammonium molybdate tetrahydrate is selected).

[0059] (5) The rare earth metal source includes any one or more of yttrium salt, lanthanum salt, scandium salt or cerium salt. The yttrium salt includes yttrium nitrate, the lanthanum salt includes lanthanum nitrate, the scandium salt includes scandium nitrate, and the cerium salt includes cerium nitrate.

[0060] S20, after heating and co-precipitation of the precursor solution, the precursor RE-NiMoOH is obtained by separation, including the following sub-steps S21-S23:

[0061] S21, the round-bottom flask containing the precursor solution is placed in an oil bath, the reaction temperature is 150 ℃, the reaction time is 30 min, and after the reaction is completed and the temperature is reduced to room temperature, the precipitate is the precursor RE-NiMoOH.

[0062] S22, the system obtained in step S21 is washed with anhydrous ethanol, a total of 3 times. Then the washed system is centrifuged at 5000 rpm for a total of 3 min using a centrifuge, and the light green precipitate (precursor RE-NiMoOH) is separated out.

[0063] S23, the light green precipitate obtained in step S22 is vacuum freeze-dried at -70 ℃ for 12 h to obtain a light green powder, and the precursor RE-NiMoOH powder is obtained by grinding.

[0064] S30, the precursor RE-NiMoOH powder is annealed under a reducing atmosphere to obtain a nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolysis water hydrogen production, and the specific operation is as follows:

[0065] The precursor RE-NiMoOH powder is placed in a tube furnace and calcined at 400 ℃ for 1 h in a 0.55 wt% H2 / Ar mixed gas, with a heating rate of 5 ℃ / min, and the precursor RE-NiMoOH powder is finally converted into Ni4Mo@RE-MoO 3-x As a nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolysis water hydrogen production.

[0066] The embodiment also provides a nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolysis water hydrogen production, which is prepared by the preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolysis water hydrogen production in the embodiment.

[0067] The embodiment also provides an application of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water in hydrogen production by alkaline electrolysis of water: taking the substrate coated with the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water as a working electrode.

[0068] Test Example 1

[0069] The test example uses one of the nickel-molybdenum-based rare earth element doped core-shell catalysts for hydrogen production by alkaline electrolysis of water in the embodiment for actual testing.

[0070] Specifically, the test example uses the preparation method of one of the nickel-molybdenum-based rare earth element doped core-shell catalysts for hydrogen production by alkaline electrolysis of water in the embodiment, and 7 nickel-molybdenum-based rare earth element doped core-shell catalysts are prepared, which are respectively recorded as catalyst 1, catalyst 2, catalyst 3, catalyst 4, catalyst 5, catalyst 6 and catalyst 7. Two comparative samples are prepared, which are recorded as comparative sample 1 and comparative sample 2.

[0071] The specific process parameters in the preparation process of the above 7 nickel-molybdenum-based rare earth element doped core-shell catalysts for hydrogen production by alkaline electrolysis of water and the 2 comparative samples are shown in Table 1.

[0072] Table 1 (specific process parameters in the preparation process of catalyst 1, catalyst 2, catalyst 3, catalyst 4, catalyst 5, catalyst 6, catalyst 7, comparative sample 1 and comparative sample 2)

[0073]

[0074] Figure 2 The XRD pattern of catalyst 1, comparative sample 1 and comparative sample 2 of Test Example 1 of the present application is shown in the following figure.

[0075] As shown in (a) and (b) of FIG. 1, PDF#03-1036 and PDF#04-0850 are X-ray diffraction standard cards published by the Joint Committee on Powder Diffraction Standards (JCPDS), corresponding to the crystal structure of Ni4Mo and Ni. As shown in (a) of FIG. 1, the XRD pattern of comparative sample 1 presents three main diffraction peaks, respectively located at 44.17°, 51.34° and 75.85°, which are analyzed to belong to the (121), (310) and (312) crystal planes of Ni4Mo alloy. As shown in (b) of FIG. 1, the XRD pattern of comparative sample 2 presents three main diffraction peaks, respectively located at 44.48°, 51.54° and 75.86°, which are analyzed to belong to the (121), (310) and (312) crystal planes of Ni4Mo alloy. Figure 2 Figure 2 As shown in (a) of FIG. 1, the XRD pattern of comparative sample 1 presents three main diffraction peaks, respectively located at 44.17°, 51.34° and 75.85°, which are analyzed to belong to the (121), (310) and (312) crystal planes of Ni4Mo alloy. As shown in (b) of FIG. 1, the XRD pattern of comparative sample 2 presents three main diffraction peaks, respectively located at 44.48°, 51.54° and 75.86°, which are analyzed to belong to the (121), (310) and (312) crystal planes of Ni4Mo alloy. Figure 2 ​As shown in section (b), in the XRD pattern of comparison sample 2, the diffraction peaks at 44.8°, 51.84°, and 76.31° correspond to the (111), (200), and (220) crystal planes of Ni, respectively, indicating the successful synthesis of Ni. When a trace amount of Y doping was introduced into the Ni4Mo matrix, XRD tests showed that the characteristic diffraction peaks of the Ni4Mo bulk phase did not undergo significant crystal structure changes, but the peak positions shifted towards smaller angles, indicating an increase in lattice spacing. This change in lattice parameters is attributed to the Y... 3+ The ionic radius (89 pm) is greater than that of Ni. 2+ Ionic radius (72 pm) and Mo 6+ The ionic radius (65 pm) induces lattice distortion during the doping process.

[0076] Figure 3 This is a SEM image of catalyst 1 in Test Example 1 of the present invention.

[0077] like Figure 3 As shown, catalyst 1 clearly exhibits a stacked nanoparticle structure. Combined with the mass fraction and atomic fraction test data of each element in catalyst 1 in Table 2 below, the measured composition of each element shows an approximate agreement with the theoretical ratio, further confirming the controllability and uniformity of element doping and distribution during the synthesis of the core-shell structure material of catalyst 1. This atomic-level uniform elemental dispersion characteristic provides structural assurance for the synergistic catalytic effect of the catalyst's active sites.

[0078] Table 2 (Elemental mass percentage and atomic percentage of each element in catalyst 1)

[0079]

[0080] Figure 4 These are TEM images of catalyst 1 in Test Example 1 of the present invention. Part a is a low-magnification TEM morphology image, and part b is a high-resolution transmission electron microscopy (HRTEM) image.

[0081] like Figure 4 As shown in section a, catalyst 1 is Ni4Mo@Y-MoO 3-x It has a core-shell nanoparticle structure with an average particle size of approximately 9 nm.

[0082] like Figure 4 As shown in section b, 0.19 nm and 0.215 nm correspond to the (121) crystal plane of Ni4Mo and the (220) crystal plane of MoO3, respectively. In particular, the lattice spacing of the MoO3 (220) crystal plane increases from 0.214 nm to 0.215 nm. This phenomenon confirms that Y has been successfully doped into the material, which complements the conclusion of lattice displacement observed by XRD.

[0083] Figure 5 These are the XPS and EPR spectra of each element in catalyst 1 and control sample 1 of test example 1 of the present invention.

[0084] like Figure 5 As shown:

[0085] (1) In the fine XPS spectrum of the 2p orbital of Ni element in catalyst 1, the characteristic peaks at 851.61 eV and 868.85 eV correspond to Ni, respectively. 0 2p 3 / 2 Characteristic peaks and Ni 0 2p 1 / 2 Characteristic peaks indicate the synthesis of Ni4Mo alloy under hydrogen reduction. Furthermore, characteristic peaks at 855.22 eV and 872.82 eV correspond to Ni... 2+ 2p 3 / 2 Characteristic peaks and Ni 2+ 2p 1 / 2 Characteristic peaks, which are attributed to the inevitable oxidation in the air.

[0086] (2) In the XPS fine spectrum of the 3d orbitals of Mo, the characteristic peaks at 227.19 eV and 229.58 eV correspond to Mo. 0 3D 5 / 2 Characteristic peaks and Mo 0 3D 3 / 2 Characteristic peaks; the characteristic peaks at 228.44 eV and 232.36 eV correspond to Mo. 4+ 3D 5 / 2 Characteristic peaks and Mo 4+ 3D 3 / 2 Characteristic peaks; the characteristic peaks at 231.45 eV and 234.57 eV correspond to Mo. 6+ 3D 5 / 2 Characteristic peaks and Mo 6+ 3D 3 / 2 Characteristic peaks.

[0087] (3) In the fine XPS spectrum of the 3d orbitals of Y, the characteristic peaks at 157.1 eV and 159.2 eV correspond to the 3d orbitals of Y. 5 / 2 Characteristic peaks and 3d Y 3 / 2 Characteristic peaks indicate that Y exists in a stable chemical state in Ni4Mo@Y-MoO in catalyst 1. 3-x In composite materials, it is particularly noteworthy that, compared to Ni4Mo in control sample 1, the Ni4Mo@Y-MoO in catalyst 1... 3-x Ni in 0 2p 3 / 2 Characteristic peaks and Ni0 2p 1 / 2 The characteristic peak shifted to low binding energy by 0.32 eV, while Mo 0 3d 5 / 2 The characteristic peak shifted to low binding energy by 0.32 eV, while Mo 0 3d 3 / 2 The characteristic peak shifted to high binding energy by 0.16 eV, which clearly revealed that Ni 0 The decrease of binding energy indicated the increase of its surrounding electron cloud density, while Mo 0 The increase of binding energy reflected the decrease of its electron density, and the electron was transferred from Mo to Ni, which was the charge redistribution mechanism closely related to the doping regulation of Y.

[0088] (4) The XPS characteristic peak of 1s orbit of O element can be divided into three parts, which are lattice oxygen O α (529.75 eV), oxygen vacancy O β (530.54 eV) and surface adsorbed oxygen O γ (531.54 eV), and the EPR spectrum showed that Ni4Mo@Y-MoO 3-x of catalyst 1 had strong oxygen vacancy signal, while Ni4Mo of comparative sample 1 had no oxygen vacancy signal, and the content of oxygen vacancy was further estimated by peak area analysis method, as shown in Table 3, the content of oxygen vacancy in Ni4Mo@Y-MoO 3-x of catalyst 1 was about 38.74%.

[0089] Table 3 (percentage of fitted peak area of O 3-x , O α and O β of Ni4Mo@Y-MoO γ of catalyst 1 obtained from XPS spectrum of 1s orbit of O element)

[0090]

[0091] Test Example 2

[0092] This test example 2 is based on the embodiment and test example 1, and the performance of the nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolysis water hydrogen production is tested in the actual alkaline electrolysis water hydrogen production.

[0093] Specifically in this test example 2, the electrochemical performance of catalyst 1, catalyst 2, catalyst 3, catalyst 4, catalyst 5, catalyst 6, catalyst 7, comparative sample 1, comparative sample 2 and commercial 20% Pt / C (hereinafter, the above 10 samples are collectively referred to as “first catalyst powder”) is tested.

[0094] The test / operation method is as follows: The test / operation method is as follows:

[0095] A01, 4 mg of the first catalyst powder and 1.2 mg of carbon powder were weighed respectively and dispersed in 1 mL of anhydrous ethanol to obtain dispersion 1, 21 μL of 10 wt% Nafion solution was added to the above dispersion, and ultrasonic dispersion was carried out in an ice water bath for 2 min to obtain dispersion 2.

[0096] A02, 1 μL of dispersion 2 was coated on a rotating disc electrode with a diameter of 5 mm using a pipette, and a film was obtained after natural drying at room temperature.

[0097] A03, a graphite rod was used as the counter electrode, Hg / HgO was used as the reference electrode, and the electrode prepared in step A02 was used as the working electrode, and a three-electrode electrochemical test was carried out in 1 mol / L KOH solution, the rotation speed was 1600 rpm, the scanning window was -0.8 V to -2 V (relative to the reversible hydrogen potential), and the scanning rate was 5 mV / s.

[0098] The above steps A01-A03 were repeated 10 times, and the first catalyst powder was tested as catalyst 1, catalyst 2, catalyst 3, catalyst 4, catalyst 5, catalyst 6, catalyst 7, comparative sample 1, comparative sample 2, and commercial 20% Pt / C.

[0099] Figure 6 The LSV test curve of the working electrode provided by catalyst 1, catalyst 2, catalyst 3, catalyst 4, and commercial 20% Pt / C in test example 2 of the present application.

[0100] As shown in Figure 6 , the electrode potential of the working electrode provided by catalyst 1, catalyst 2, catalyst 3, and catalyst 4 was 53 mV, 113 mV, 133 mV, and 259 mV, respectively, at a current density of 10 mA / cm 2

[0101] Figure 7 The LSV test curve of the working electrode provided by catalyst 1, catalyst 5, catalyst 6, catalyst 7, and commercial 20% Pt / C in test example 2 of the present application. Figure 8 The LSV test curve of the working electrode provided by catalyst 1, commercial 20% Pt / C, comparative sample 1, and comparative sample 2 in test example 2 of the present application.

[0102] As shown in Figure 6 , Figure 7 , and Figure 8 :

[0103] ​(1) The working electrode provided by catalyst 5, catalyst 6, and catalyst 7 has an electrode potential of 64 mV, 70 mV, and 77 mV, respectively, at a current density of 10 mA / cm 2 Although all of them are lower than the Ni4Mo alloy (127 mV) of the comparative sample 1, it indicates that rare earth element doping is generally beneficial to improving the Ni4Mo catalytic activity, but the performance is still inferior to that of the catalyst 1 (53 mV) of the Y-doped system, further highlighting the optimal optimization effect of trace Y doping on the hydrogen evolution performance of Ni4Mo.

[0104] (2) The working electrode provided by the comparative sample 1 and the comparative sample 2 has an electrode potential of 127 mV and 352 mV, respectively, at a current density of 10 mA / cm 2 From the results, it can be analyzed that the activity of the catalyst 1 (53 mV) is much higher than that of the comparative sample 1 (127 mV) and the comparative sample 2 (352 mV), and the overpotential is reduced by 58.3% and 84.9%, respectively, which proves that trace Y doping can synergistically optimize the d-band center of NiMo, accelerate the Volmer-Heyrovsky step kinetics, and especially when the Y doping amount is ≤0.1 mmol (catalyst 1 and catalyst 2), the performance is better than that of the traditional Ni4Mo alloy (comparative sample 1).

[0105] Test Example 3

[0106] In this test example 3, the performance of the nickel-molybdenum-based rare earth element doped core-shell catalyst for alkaline electrolytic water hydrogen production when applied in alkaline electrolytic water hydrogen production is actually tested based on the embodiment and test example 1.

[0107] In this test example 3, the electrochemical stability of the catalyst 1, the catalyst 5, the catalyst 6, the catalyst 7, the comparative sample 1, and the comparative sample 2 (hereinafter collectively referred to as “second catalyst powder”) is tested.

[0108] The test / operation method is as follows:

[0109] B01, 20.4 mg of the second catalyst powder and 136 mg of the 5wt% Nafion solution were weighed and dispersed in 30 ml of a 1:1 mixed solution of isopropanol and water, and ultrasonic dispersion was performed in an ice water bath for 10 min to obtain a dispersion liquid 3.

[0110] B02, the dispersion liquid 3 was sprayed on a hydrophobic carbon paper with an area of 2 cm×2 cm by an ultrasonic spraying machine, and the flow rate was set to 0.5 mL / min. During the spraying process, the hydrophobic carbon paper needs to be placed on a heating plate at 80°C to ensure sufficient drying and coating formation, and after drying, the hydrophobic carbon paper is cut into 1 cm×1 cm size as an electrode sheet.

[0111] B03, graphite rod as the counter electrode, Hg / HgO as the reference electrode, the electrode piece obtained in step B02 as the working electrode, and a three-electrode electrochemical stability test was carried out in 1 mol / L KOH solution.

[0112] The above steps B01-B03 were repeated for 6 times, and tests were carried out on the second catalyst powder as catalyst 1, catalyst 5, catalyst 6, catalyst 7, comparative sample 1 and comparative sample 2, respectively.

[0113] Figure 9 is the hydrogen evolution stability test curve of the working electrode provided by catalyst 1, catalyst 5, catalyst 6, catalyst 7, comparative sample 1 and comparative sample 2 in test example 3 of the present application.

[0114] As shown in Figure 9 , the working electrodes provided by catalyst 1, catalyst 5, catalyst 6 and catalyst 7 can be stably cycled for 300 h (1 M KOH, 25℃) at a current density of 10 mA / cm 2 Under the same conditions, the working electrodes provided by comparative sample 1 and comparative sample 2 have poor stability, which indicates that the nickel-molybdenum-based rare earth element doped core-shell catalyst provided by the embodiments has greater stability advantage than other catalysts without rare earth element doping.

[0115] Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a nickel-molybdenum-based rare earth element-doped core-shell catalyst for hydrogen production by alkaline electrolysis of water, characterized by, Comprising the following steps: S10, dissolving nickel salt, molybdate and rare earth metal source in a mixed solution of ethylene glycol containing ammonia water according to the molar ratio of 2:0.5:(0.035~1), to obtain a precursor solution with a rare earth metal source concentration of 0.5 mol / L~1.0 mol / L, Wherein, the rare earth metal source includes any one or more of yttrium salt, lanthanum salt, scandium salt or cerium salt, and the NH3 concentration in the precursor solution is 0.5 wt%~1.0 wt%; S20, after heating the precursor solution at 100 ℃~200 ℃ for 15 min~60 min for co-precipitation reaction, separating out the precursor RE-NiMoOH; S30, annealing the dried fine powdery precursor RE-NiMoOH at 300-500 DEG C for 1-2 h in a reducing atmosphere to obtain Ni4Mo@RE-MoO 3-x As a nickel-molybdenum-based rare earth element-doped core-shell catalyst for hydrogen production by alkaline electrolysis of water, The nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis water has a Ni4Mo alloy core and a RE-MoO 3-x shell layer.

2. The preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to claim 1, characterized in that: wherein In step S10, the nickel salt includes nickel nitrate, the molybdate includes ammonium molybdate, the yttrium salt includes yttrium nitrate, the lanthanum salt includes lanthanum nitrate, the scandium salt includes scandium nitrate, and the cerium salt includes cerium nitrate.

3. The preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to claim 1, characterized in that: wherein, In step S10, the rare earth metal source is yttrium salt, The molar feeding ratio of the nickel salt, the molybdate and the rare earth metal source is 2:0.5:(0.035~0.045).

4. The preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to claim 1, characterized in that: wherein In step S10, the ethylene glycol concentration in the precursor solution is 80 wt%~90 wt%.

5. The preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to claim 1, characterized in that: wherein In step S20, the separation method is: After washing with anhydrous ethanol, vacuum freeze-drying and grinding to fine powder.

6. The preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to claim 5, characterized in that: wherein The vacuum freeze-drying temperature is -60 ℃ to -70 ℃, and the time is 10 h~20 h.

7. The preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to claim 1, characterized in that: wherein In step S30, the reducing atmosphere is a mixed gas of hydrogen and argon, The hydrogen concentration in the mixed gas is 0.2 wt%~0.6 wt%.

8. The preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to claim 1, characterized in that: wherein, In step S30, the heating rate of annealing is 3 ℃ / min~5 ℃ / min.

9. A nickel-molybdenum-based rare earth element-doped core-shell catalyst for hydrogen production by alkaline electrolysis of water, characterized by, Prepared by the preparation method of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to any one of claims 1~8.

10. The application of the nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water according to claim 9 in hydrogen production by alkaline electrolysis of water, wherein, The nickel-molybdenum-based rare earth element doped core-shell catalyst for hydrogen production by alkaline electrolysis of water is coated on a substrate, thereby serving as a working electrode in hydrogen production by alkaline electrolysis of water together with the substrate.

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